As known, an axial bearing arrangement for a drive shaft of a centrifugal compressor may include:                a first axial bearing plate and a second axial bearing plate, also named first and second thrust plates, being parallel and each having an annular ring shape, the first axial bearing plate having a first surface axially facing the second axial bearing plate and a second surface opposite to the first surface of the first axial bearing plate, the second axial bearing plate having a first surface axially facing the first axial bearing plate and a second surface opposite to the first surface of the second axial bearing plate,        a spacer ring clamped between the first surfaces of the first and second axial bearing plates at radial outer portions of the first and second axial bearing plates, the spacer ring defining an axial distance between the first and second axial bearing plates, and        a bearing sleeve being secured to a compressor block and abutting the second surface of the second axial bearing plate, so as to tighten the first and second axial bearing plates and the spacer ring against a contact surface provided on the compressor block.        
In operation, a radial flange portion of the drive shaft extends into a space defined between inner surface of the spacer ring and radial inner portions of the first surfaces of the first and second axial bearing plates, and cooperates with the first surfaces of the first and second axial bearing plates in order to limit an axial movement of the drive shaft.
In such a compressor, especially when operating at very high speed, high temperature conditions may occur, inducing thermal stress and deformations in compressor components, e.g. when components of different thermal expansion materials are secured to each other and/or when there is large thermal gradient in solid parts.
Especially critical is the axial bearing arrangements, where the radial flange portion of the drive shaft rotates between the first and second axial bearing plates, with very small clearances between rotating and fixed parts.
Mechanical stress introduced into the axial bearing arrangement through tolerances in mounting and assembling of the compressor or due to above-mentioned non-uniform thermal expansion may deteriorate the parallel positioning of the first and second axial bearing plates. This can lead to seizure of the axial bearing arrangement and shortened lifetime of the centrifugal compressor.